| The free-form surfaces are widely used in industrial field,and grinding technology can greatly affect the final surface quality of free-form workpieces.At present,freeform surface grinding is still mainly manual,leading to low efficiency.In order to ensure the grinding quality and improve efficiency,robot off-line grinding has gradually become mainstream processing method instead of human work.In the process of grinding,the robot path planning is a core technology for off-line system.In this paper,off-line programming software system with giriding simulation environment which is based on ROS open source platform and fusion of path planning,is formed and experimentally verified,which is studied in this paper as follows:Firstly,this paper simplified and analyzed the grinding robot model,and established the coordinate system of six axes such as base,big arm and hand.Through the geometric relationship between the connecting rods and the determination of the joints,the forward-inverse kinematics of the robot was analyzed and modeled by spatial screw theory.The pose of end-grinder was obtained by joint angle while model was established completely.In order to verify the result of inverse kinematics,it's important to build forward-inverse kinematics and analysis the data of pose by Matlab toolbox.After the step of kinematics analysis,the simulation platform of grinding based on ROS operation system was established,and the URDF file was completed with the assistant of plugins in Solid Works,and the robot simulation model was obtained when file was loaded correctly which including arm information such as startup file in this platform.It's essential to complete the configuration of the robot-motion model based on the robot visualization tool in RVIZ.According to the interface function of ROS package,robot model got the corresponding program of nodes in the motion process to compiled files and realized the simulation motion.Correct simulation motion of the robot was verified by typical interpolation of linear and circular,so as to ensure the accuracy of the robot motion.Secondly,the trajectory planning of grinding robot was studied under Cartesian coordinate.According to the characteristics of free-form surface,the appropriate method with grinding and trajectory planning needed to be selected for complex workpiece.The point cloud datas of the workpiece were obtained according to the laser scan,and the discrete points formed the contour.The NURBS curve was used for trajectory planning after contour of discrete points were obtained.According to S-type velocity curve,the interpolation sequence of trajectory points were completed.For the curvature problem,the bow height error adaptive algorithm was used to optimize motion that can ensure the accuracy of the robot motion.Finally,this paper designs and develops offline programming system software for free-form surfaces using the ROS open source platform and the Qt open source library,etc.Functional module was customized and packaged through signal slots and interfaces in ROS.Then the optimized interpolated pose was obtained by adaptive algorithm mentioned above,and code conversion were performed under this platform.The correctness of planning algorithm and the practicability of the software system were verified by simulation experiments. |
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